Title:
EW[OIII] as an orientation indicator for quasars: implications for the torus

Abstract: We present an analysis of the average spectral properties of 12,000 SDSS
quasars as a function of accretion disc inclination, as measured from the
equivalent width of the [O III] 5007{\AA} line. The use of this indicator on a
large sample of quasars from the SDSS DR7 has proven the presence of
orientation effects on the features of UV/optical spectra, confirming the
presence of outflows in the NLR gas and that the geometry of the BLR is
disc-like. Relying on the goodness of this indicator, we are now using it to
investigate other bands/components of AGN. Specifically, the study of the
UV/optical/IR SED of the same sample provides information on the obscuring
"torus". The SED shows a decrease of the IR fraction moving from face-on to
edge-on sources, in agreement with models where the torus is co-axial with the
accretion disc. Moreover, the fact we are able to observe the broad emission
lines also in sources in an edge-on position, suggests that the torus is rather
clumpy than smooth as in the Unified Model. The behaviour of the SED as a
function of EW[OIII] is in agreement with the predictions of the clumpy torus
models as well.

Comments:

9 pages, 3 figures, accepted for publication in Frontiers in Astronomy and Space Sciences, Research Topic "Quasars at all cosmic epochs"; proceedings of the conference "Quasars at all cosmic epochs", held in Padova, April 2-7, 2017